Table of Contents
Advertisement
Audio Input/Output Block :
Refer to the figure of Audio Signal Input/Output on page 15.
@ Analog Recording
Audio signals from the microphone or the line-in terminal are emphasized for the high-pass area
through the pre-emphasis circuit for improving the high-pass characteristics during playing.
After eliminating unnecessary band over 20KHz by the low-pass filter, signals are quantized.
FSB
signal output from LSIC turns on and off the analog switches to pick up the left and right signals
alternately.
D/A converter PCM55 is used as an analog converter during recording, and receives signals through
REC/PLAY switching relay. Every bit of the data (DAO ~ DA15) of the A/D converter compares the
input sound potential with the outpout potential.
Comp terminal of LSIC receives different voltage by the comparator consisting of the ope-amp.
By
detecting the data bits (DAO ~ DA15) when the voltage of the Comp terminal becomes 0 volt, the
analog voltage level is changed to 16 bits digital signals which is modulated into the digital IF signal
by LSI to record. This signals flows in the sequence of LSIC + LS!IA > LSIB + Pre Amp > Head >
Tape to record.
The OPL and OPR output signals from LSIC controls automatically the bias voltage level to the Ope-
Amp when recording. As the D/A converter handles analog voltage level, all bits of DAO ~ DA15
becomes 1 when receiving the maximum amplitude voltage of 4.3 volt. Adversely all bits becomes 0
when receiving the minimum voltage of —3 volt.
Normally the offset potential is set so as to make 1000 000 for DA15 ~ 0000 0000 for DAO at +0 volt
at no signal recording. To avoid fluctuation by supply voltage or temperature, the setting of the offset
voltage to +0 volt is automatically regulated by controlling voltage of the offset bias to the ope-amp
by OFL/OFR signals.
0
IN
OV
IN
Vv
-3V
aay
To be fixed after adjusted.
Potential regulation by voltage of OFLYOFR
Advertisement
Table of Contents
